## Search found 92 matches

Sun Mar 17, 2019 12:04 am
Forum: Balancing Redox Reactions
Topic: fixed values
Replies: 1
Views: 248

### Re: fixed values

When dealing with a problem that has a redox reaction, you should illustrate the individual reduction and oxidation reactions that combine to create the overall redox reaction. If the individual reactions are unclear, it can be helpful to look in the appendix to view individual reduction reactions, ...
Sat Mar 16, 2019 11:55 pm
Forum: Phase Changes & Related Calculations
Topic: boiling points
Replies: 4
Views: 333

### Re: boiling points

To get vaporized, a substance must undergo some enthalpy of vaporization at the boiling point. Therefore, simply being at the boiling point is not enough to vaporize a substance.
Sat Mar 16, 2019 6:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Solubility Product
Replies: 1
Views: 72

### Solubility Product

Question 5N.15 in the seventh edition incorporates solubility products from table GI.1. What are these? Could you explain how to incorporate them into a problem such as 5N.15 in order to solve it?
Sat Mar 16, 2019 5:48 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inclusion of ions in the cell diagram
Replies: 1
Views: 89

### Re: Inclusion of ions in the cell diagram

Ions or any other species that partake in redox reactions will be included in the cell diagram. The only species which would not be included from the redox reactions making up the overall reaction would be liquid water.
Sun Mar 10, 2019 7:17 pm
Forum: General Rate Laws
Topic: Rate Determining Step
Replies: 5
Views: 2587

### Re: Rate Determining Step

Yes, you are correct. The reaction is perceived to be occurring faster in other steps relative to the rate determining step. Therefore, the rate determining step will determine how quickly the reaction will proceed since it is the slowest. The effect of the other steps on the rate of the reaction is...
Sun Mar 10, 2019 7:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Final Exam
Replies: 23
Views: 591

### Re: Final Exam

Yes, chemical equilibria will be on the final exam.

Yes, the final exam is cumulative.
Sun Mar 10, 2019 7:08 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7th edition 7A. 17
Replies: 3
Views: 367

### Re: 7th edition 7A. 17

If you turn the concentrations given in mmol units to mole units, you will get the right answer. For example, on the top row turn each of the 1.25 mmol to 1.25*10^-3 mol. The reaction is of the fifth order. (1.25*10^3)^5 is equal to about 3.05*10^-15. When you set up the equality k(3.05*10^-15)=8.7*...
Sun Mar 10, 2019 6:42 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homework 15.61
Replies: 1
Views: 104

### Re: Homework 15.61

To solve this problem, you need to use the equation ln(k2/k1)=((activation energy)/R)((1/T1)-(1/T2)). The problem gives you the values for two different rate constants and their respective temperatures. Therefore, you can plug 0.76 s^-1 into k2 and 1000. K into T2. After that, you can plug 0.87 s^-1...
Sun Mar 03, 2019 10:26 pm
Forum: Administrative Questions and Class Announcements
Topic: Homework
Replies: 7
Views: 305

### Re: Homework

Sun Mar 03, 2019 10:08 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Replies: 73
Views: 3860

I personally enjoy attending the drop in sessions. Often my questions go unanswered in large workshops, so I like talking to people one-on-one. From my experience, drop in sessions have generally been a pretty good way to do that.
Sun Mar 03, 2019 10:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: the phases in a cell diagram
Replies: 4
Views: 161

### Re: the phases in a cell diagram

The order in which you listed them with aqueous in the middle and solids on the outside seems correct. Apart from what you have already mentioned, the book also mentions placing reactants before products when constructing cell diagrams. After you have arranged the phases as you did here, I recommend...
Sun Mar 03, 2019 6:52 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Products of Electrolysis
Replies: 1
Views: 104

### Products of Electrolysis

Some of the self test questions in the seventh edition ask for the products of electrolysis of certain compounds. Can some explain how one would find the products of electrolysis of any compound? Thank you.
Sun Mar 03, 2019 6:29 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Non-Spontaneous
Replies: 3
Views: 161

### Re: Non-Spontaneous

Electrolytic cells generally have their own spontaneous reaction that would occur if an external voltage were not applied to them. However, when a voltage is applied that provides a greater potential difference in what was previously the non-spontaneous direction, electrolysis occurs and what was pr...
Sun Mar 03, 2019 6:13 pm
Forum: Balancing Redox Reactions
Topic: balancing redox reactions
Replies: 5
Views: 180

### Re: balancing redox reactions

You will often need to balance out the oxygen atoms and hydrogen atoms in a half reaction. When you need to do this, you involve H+ and H2O. Specifically, these would be involved in a half reaction within an acidic medium so that OH- might not be included. An appropriate amount of H2O would be added...
Sun Feb 24, 2019 11:47 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: higher entropy cis or trans
Replies: 8
Views: 1199

### Re: higher entropy cis or trans

The molecule featured possesses an octahedral geometry. Consider X1, X2, X3, and X4 to span horizontally across the molecule, with odd numbers being positioned opposite from each other and even numbers being positioned opposite from each other. Now, consider Y1 and Y2 to be the points on the opposit...
Sun Feb 24, 2019 11:24 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs Free Energy Units
Replies: 5
Views: 183

### Re: Gibbs Free Energy Units

I think you should generally use kJ/mol, especially when some particular reaction is involved. That way you know that you are referring to how much energy is released or absorbed each time that reaction is performed. Other than that, look at the context of the question and the units of the values gi...
Sun Feb 24, 2019 11:15 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Galvanic Cell
Replies: 3
Views: 136

### Re: Galvanic Cell

Yes, I believe so. The solutions manual states this when explaining problem 6L.7 from the seventh edition.
Sat Feb 23, 2019 11:50 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412840

### Re: Post All Chemistry Jokes Here

Sat Feb 23, 2019 11:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell diagram
Replies: 3
Views: 148

### Re: Cell diagram

The anode will generally be on the left, and the cathode will generally be on the right.

If standard reduction potentials are given, you would reverse the oxidation reaction, namely that of the anode.
Sat Feb 23, 2019 11:38 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Moles of Gas affecting shift in equilibrium
Replies: 1
Views: 93

### Re: Moles of Gas affecting shift in equilibrium

When you have a certain amount of moles present in some equilibrium reaction per the different reactants and products involved, you will have a certain equilibrium constant. Because of PV=nRT, this also applies to gas pressure under ideal conditions. What this means is that if the number of units of...
Sun Feb 17, 2019 11:32 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Extensive Property
Replies: 3
Views: 373

### Re: Extensive Property

An extensive property is one which depends on how much of something there is. An example of an extensive property is heat capacity. Heat capacity either consists of molar heat capacity times the amount of moles present or specific heat capacity times the amount of grams present per the substance in ...
Sun Feb 17, 2019 11:12 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Residual Entropy
Replies: 2
Views: 135

### Re: Residual Entropy

I haven't come across problems incorporating what you mentioned. Since the value of W is yielded by (number of available positions)^(number of particles), then I think it's fair to assume that you will be using the value of k rather than R. W is in terms of individual particles and so is k, so I thi...
Sun Feb 17, 2019 11:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sign of Free Energy
Replies: 2
Views: 101

### Re: Sign of Free Energy

If such problem were to arise, you would need to be given specific values for enthalpy, temperature, and entropy in order to find the sign of Gibbs Free Energy. Either that, or you would need to be given some means to find those values. Without that information you would be unable to determine the s...
Sat Feb 16, 2019 11:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 4
Views: 183

### Re: Bond Enthalpies

It's a good idea to learn to draw basic Lewis structures for these types of problems. The structures for these problems are generally pretty basic, but having the image available to you can make adding and subtracting bonds much easier, even if it is rather simplistic. You don't really need to know ...
Sat Feb 16, 2019 11:48 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8047
Views: 1412840

### Re: Post All Chemistry Jokes Here

OMG

Did you hear that Oxygen and Magnesium are a couple?
Sat Feb 16, 2019 11:44 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: State Function
Replies: 2
Views: 153

### Re: State Function

The book mentions that a state function does not need to be composed of state functions itself to be a state function. Therefore, the fact that internal energy is composed of work and heat, neither of which are state functions, does not stop internal energy from being a state function. Thus, the cha...
Sat Feb 16, 2019 11:38 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Pressure Equation
Replies: 7
Views: 454

### Re: Pressure Equation

This equation would be most applicable when calculating the change in entropy from a pressure change.
Sun Feb 10, 2019 11:35 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Mondays class
Replies: 3
Views: 168

### Re: Mondays class

The class will consist of Lavelle reviewing material through the means of past exam questions.
Sun Feb 10, 2019 11:31 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Replies: 1
Views: 101

It might be useful to keep in mind that an adiabatic system will have a constant heat. As such, temperature will also be unchanging due to the insulation provided. I did not see any problems relating to this concept, but it might be useful to know what the term means, especially since both the book ...
Sat Feb 09, 2019 10:54 pm
Forum: Student Social/Study Group
Topic: midterm/homework
Replies: 2
Views: 137

### Re: midterm/homework

Gibbs free energy starts at 4J. Lavelle said in lecture that Gibbs free energy would not be covered on the midterm. The topic before Gibbs free energy is global changes in free entropy. Therefore, I would probably just do all the homework exercises up through 4I (Global Changes in Entropy) without d...
Sat Feb 09, 2019 8:55 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Average Kinetic Energy vs U?
Replies: 1
Views: 83

### Re: Average Kinetic Energy vs U?

Internal energy is composed of kinetic and potential energy. Specifically, the translational and rotational energy components of internal energy are fully composed of kinetic energy, while the vibrational component is composed of both kinetic and potential energy. U(m) = 3/2nRT because the internal ...
Sat Feb 09, 2019 8:41 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When n is not given
Replies: 3
Views: 146

### Re: When n is not given

If the question requires you to use moles, it will give you that information or the information necessary to find the number of moles. Is there a specific question which you may be referencing?
Sat Feb 02, 2019 11:15 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U
Replies: 4
Views: 160

### Re: Delta U

Delta U can be calculated by adding q and w. Since we are just finding the change in internal energy, delta U can be understood as a state function regardless of what its components might be because we are just concerned with finding the differences between final and initial conditions.
Sat Feb 02, 2019 11:11 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Equation Specific Heat Capacity
Replies: 2
Views: 102

### Re: Entropy Equation Specific Heat Capacity

You will know to use this based on whether you are dealing with ideal gas conditions and based on what kind of information you are given relating to heat capacity.

The information given in terms of constant volume or constant pressure should also help determine what you need.
Sat Feb 02, 2019 11:08 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Material on Midterm?
Replies: 9
Views: 344

### Re: Material on Midterm?

Since the midterm will cover entropy, I think at least some, if not all, of the material within the sections of 2nd and 3rd laws of thermodynamics will be covered. However, I recommend just going to lecture to listen to specific things Lavelle goes over to get a solid grasp of exactly what you will ...
Sun Jan 27, 2019 11:48 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Work, state property
Replies: 3
Views: 142

### Re: Work, state property

What this means is that you have to take into account intermediate steps when accounting for the total work performed rather than the total change between the initial and final states.
Sun Jan 27, 2019 10:40 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: State Function?
Replies: 3
Views: 152

### Re: State Function?

Adding on to the previous explanation, something that is not a state function would be work. Going from one place to another may done differently, and therefore different amounts of work may be required to get from one place to another. On the other hand, enthalpy has no such possibilities for alter...
Fri Jan 25, 2019 7:55 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Le Chatelier's Principle question
Replies: 4
Views: 226

### Re: Le Chatelier's Principle question

Changing pressure by adding inert gas does not affect the reaction. It may slow down the reaction's rate somewhat, but it will not affect the equilibrium constant or the reaction quotient. On the other hand, changing pressure by altering volume does alter the reaction quotient. Concentration in term...
Wed Jan 16, 2019 2:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework #89 Ch.11
Replies: 1
Views: 71

### Re: Homework #89 Ch.11

A changes from about 27.5 to about 17.5. C changes from 0 to 10. B changes from 0 to 5. If the change in values is understood as X, then X = 5. B's value increased by X, whereas the values of A and C both changed by 2X. Therefore, K = ([2X]^2[X])/[27.5-2X]^2 in the form of ([C]^c[B]^b)/[A]^a. As see...
Wed Jan 16, 2019 2:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 6th Edition 12.59
Replies: 2
Views: 226

### Re: 6th Edition 12.59

Because the question asks for the percentage protonation of the following solutes, then you can assume that the solutes that are given are bases. Bases can become protonated whereas acids become deprotonated.
Wed Jan 16, 2019 1:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Expansion...
Replies: 2
Views: 103

### Re: Expansion...

I think what this means is that pressure is decreasing through an increase in volume.

In response to such an increase of volume, the concentration or partial pressure values of the gasses your reaction depends on would decrease.
Wed Jan 16, 2019 1:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition Question 6A.21
Replies: 1
Views: 84

### Re: 7th Edition Question 6A.21

Yes, you would assume that the concentration of the hydronium ions equals that of hydroxide ions.
Wed Jan 16, 2019 2:07 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 6A.19
Replies: 2
Views: 125

### Re: 7th Edition 6A.19

I was also confused about this. I assumed this may have just been an error in the book.
Fri Jan 11, 2019 7:47 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Concentrations when k < 10^-3
Replies: 2
Views: 95

### Re: Calculating Equilibrium Concentrations when k < 10^-3

I believe you are free to make the approximation you mentioned both in quadratics and cubics. The source for my answer is question 5I.29. The equation would have ended up being a quadratic, but the solutions manual displayed usage of the aforementioned approximation.
Fri Jan 11, 2019 7:43 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc of the Forward/Reverse Reaction
Replies: 6
Views: 2039

### Re: Kc of the Forward/Reverse Reaction

The Kc of the reverse reaction is related to the Kc of the forward reaction because these two values are reciprocals of each other.

If the Kc of the forward reaction is X, then the Kc of the reverse reaction is 1/X.
Fri Jan 11, 2019 7:39 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Using Q
Replies: 1
Views: 50

### Re: Using Q

Q is the reaction quotient. You can find Q just as you would find K by finding the ratio aA<>bB as [B]^b/[A]^a. Q can give you a ratio of products to reactants, which you can then compare to K in order to see where the reaction will head in order to reach equilibrium, expressed as the value of K. If...
Thu Jan 10, 2019 6:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.5
Replies: 2
Views: 97

### Re: 5G.5

I think the flasks are displayed in chronological order from left to right. Therefore, the reaction is at equilibrium in both flasks 3 and 4. However, because flask 3 occurs first, it displays the point in time when the reaction first reached equilibrium. By the time the reaction reached the state d...
Thu Jan 10, 2019 6:20 pm
Forum: Ideal Gases
Topic: Temperature Units
Replies: 4
Views: 81

### Re: Temperature Units

I think it depends on what the question gives you. For example, take a look at 5H.3 in the seventh edition. It specifically asks you to take into consideration the equilibrium constants for reactions occurring at 300K, despite the fact that all the products and reactants in the reactions are gases. ...
Thu Jan 10, 2019 5:58 pm
Forum: Ideal Gases
Topic: Temperature Units
Replies: 4
Views: 81

### Re: Temperature Units

I believe Lavelle mentioned in one of the modules that the temperature will be given to you. You will not have to assume which is correct.
Thu Jan 10, 2019 5:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE tables with initial values products
Replies: 1
Views: 31

### Re: ICE tables with initial values products

If there had been initial values for ADP or Pi, you would have added those values to the change each individual value underwent in order to find their equilibrium values. When finding the equilibrium value for the molarity of a particular substance, add the change in molarity to the initial value of...
Sat Dec 08, 2018 3:07 pm
Forum: Bronsted Acids & Bases
Topic: Test topic
Replies: 1
Views: 88

### Re: Test topic

I think it would be a good idea to memorize the more common acids that show up. However, my TA said that Lavelle told her we should not have to worry too much about memorization. Regardless, I recommend you do some memorizing just to be safe.
Sat Dec 08, 2018 2:55 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: strength of base
Replies: 8
Views: 380

### Re: strength of base

If something is a strong acid, then it will be a weaker base. Weaker acids will also be stronger bases.
Sat Dec 08, 2018 2:44 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Electronegativity & Acid Strength
Replies: 2
Views: 132

### Re: Electronegativity & Acid Strength

When comparing the strengths of acids such HOI and HOCl, the electronegativities of the Cl or I ions is important because these atoms pull electrons away from the HO bond toward themselves. This weakens the bond between the O and H atoms. The weaker the bond is, the stronger the acid will be since i...
Tue Dec 04, 2018 8:11 pm
Forum: Lewis Acids & Bases
Topic: Acid but acidity is not due to its disassociation
Replies: 1
Views: 128

### Re: Acid but acidity is not due to its disassociation

When Boron accepts lone pairs from water in the form of OH-, it is acting as a Lewis acid. After all, a Lewis acid is defined as an acid which accepts lone pairs.

Rather than being a Bronsted acid which donates protons, it is a Lewis acid that accepts electron pairs.
Sun Dec 02, 2018 6:34 pm
Forum: Naming
Topic: Naming and Charges
Replies: 1
Views: 107

### Re: Naming and Charges

You add an -ate at the end if the coordination complex as a whole has a negative charge.
Sun Dec 02, 2018 6:30 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 7th edition 3F.13
Replies: 1
Views: 118

### Re: 7th edition 3F.13

Bond angles in a tetrahedral structure are approximately 109.5 degrees. Bond length depends on the atoms themselves. Therefore, bonds between different types of atoms can have different lengths. For example, due to the fact atoms with larger atomic radii tend to have longer bonds, a bond between a s...
Sun Dec 02, 2018 5:22 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Definition of Ligand
Replies: 2
Views: 96

### Re: Definition of Ligand

The ligand is the molecule which binds to the transition metal in a coordination complex. Therefore, in response to your question, the status of ligand is conditional. It is granted to the molecule based on whether it has bonded to the central metal ion or atom.
Sun Nov 25, 2018 7:43 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Electron density
Replies: 3
Views: 354

### Re: Electron density

Yes, I believe they do. Finding the hybrid orbitals of an atom can thus be facilitated by knowing beforehand how many regions of electron density are around it.
Sun Nov 25, 2018 7:22 pm
Forum: Properties of Light
Topic: Speed of light
Replies: 13
Views: 3213

### Re: Speed of light

I have had no issue using 3.0*10^8 m/s on my exams. I recommend asking your TA about the problem you missed to see what they recommend.
Sun Nov 25, 2018 7:17 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 3
Views: 126

### Re: Polarity

You can determine whether a molecule is polar based on its symmetry. For example, if you have a trigonal planar structure with BCl3, then you know it will be nonpolar because the partial negative charges of the Cl atoms will be positioned symmetrically in such a manner that they cancel out. On the o...
Sun Nov 25, 2018 4:00 am
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.9
Replies: 1
Views: 56

### Re: 2E.9

The molecular shape of ICl3 is T-shaped. Therefore, because of the repulsion exerted by the two lone pairs the bond angle of ClICl should be slightly less than 90 degrees between a Cl atom located in the axial position and the Cl atom in the equatorial position.
Sun Nov 18, 2018 6:47 pm
Forum: Bond Lengths & Energies
Topic: VSEPR Model Question
Replies: 2
Views: 160

### Re: VSEPR Model Question

You must remember to take into account the area of electron density present due to the lone pair of nitrogen. Nitrogen has 5 valence electrons. It uses 1 to make a covalent bond with fluorine and 2 to make a covalent bond with oxygen. After using 3, it has 2 remaining. These two create a trigonal pl...
Sun Nov 18, 2018 6:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 7th edition 2E. 21
Replies: 4
Views: 116

### Re: 7th edition 2E. 21

I think it would be good to know the exact angles of the trigonal pyramidal structure. However, saying less than 109.5 should probably suffice if you don't know it since Lavelle already said we don't need to know the specific value.
Sun Nov 18, 2018 6:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Writing Bond Angles with Multiple Central Angles
Replies: 2
Views: 84

### Re: Writing Bond Angles with Multiple Central Angles

You know you would be unable to do C-C because that doesn't have an angle. That's just a bond. Triangles have angles on their corners because there are lines pointing in two different directions from each corner. If you tried to find the angle of the bond between two atoms you would just get 180 deg...
Sun Nov 18, 2018 6:09 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem Community Posts
Replies: 3
Views: 170

### Re: Chem Community Posts

I recommend asking a TA or Lavelle specifically about this. However, the syllabus itself says we can receive 3 points per week from the weekly online discussion. Therefore, I would assume that the intent behind this is that you are active on a weekly basis. Based on that assumption, I would arrive a...
Sun Nov 18, 2018 6:02 pm
Forum: Dipole Moments
Topic: Dipole moments in terms of very electronegative atoms
Replies: 3
Views: 155

### Re: Dipole moments in terms of very electronegative atoms

Yes, it would be polar since the dipole interactions would not cancel out. Overall, this molecule would experience a net dipole moment, and it would be polar.
Sun Nov 11, 2018 7:08 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 9
Views: 410

### Re: Bond Length

I think finding an average of the given bond values is the best way to find the bond length in the resonance structure. It may not be necessarily exact or equal to the actual observed value, but it should be fairly close.
Sun Nov 11, 2018 7:07 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Interionic/Intermolecular Forces
Replies: 3
Views: 236

### Re: Interionic/Intermolecular Forces

Dipole-Dipole interactions, Induced-Dipole Induced-Dipole interactions, hydrogen bonds, etc are responsible for binding molecules of different substances together. The more of these you have and the stronger they are, they more tightly bound this substance will be. For example, because H2S lacks hyd...
Sun Nov 11, 2018 7:00 pm
Forum: Ionic & Covalent Bonds
Topic: Differentiating between Covalent and Ionic
Replies: 3
Views: 176

### Re: Differentiating between Covalent and Ionic

You can know the difference between them by electronegativity difference. If the electronegativity difference between the atoms involved in a bond is 2 or above, you know the bond is ionic. If the difference is 1.5 or below, then you know it's covalent. Professor Lavelle said the area in between 2 a...
Sun Nov 11, 2018 6:49 pm
Forum: Ionic & Covalent Bonds
Topic: Partial Charges Question
Replies: 2
Views: 134

### Re: Partial Charges Question

Yes, you are correct. However, if the difference in electronegativity is over 2, you should consider the bond to be ionic.
Sun Nov 11, 2018 6:40 pm
Forum: Ionic & Covalent Bonds
Topic: hydrogen bonds and melting points
Replies: 3
Views: 107

### Re: hydrogen bonds and melting points

Hydrogen bonds can exist between hydrogen and nitrogen, oxygen, or fluorine atoms. Because H2O possesses hydrogen bonds in addition to covalent bonds, it can stick together better than H2S. Therefore, it has a higher melting point.
Sun Nov 04, 2018 5:47 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 6915

### Re: MIDTERM PRACTICE - Garlic Bread Review Session[ENDORSED]

For 8b, why can't you use Ek = hc/λ to find the kinetic energy then proceed to solve for frequency using this value + the work function all over h? The variable c incorporates the speed of light into the equation, but ejected electrons cannot travel at the speed of light. Therefore this cannot work...
Sun Nov 04, 2018 3:40 am
Forum: General Science Questions
Topic: Midterm
Replies: 3
Views: 208

### Re: Midterm

My TA said the midterm would be about as difficult as Test 2. I don’t know how this compares to the homework problems, but I suggest you do as many as possible to prepare. The concepts in the homework problems should at least be similar.
Fri Nov 02, 2018 3:39 pm
Forum: Ionic & Covalent Bonds
Topic: Highly Distorted Electrons?
Replies: 3
Views: 103

### Re: Highly Distorted Electrons?

What this means is that in ionic bonds, the cation may distort the electrons on the anion. Although this is an ionic bond in which the anion has pulled the electrons away from the cation, the cation's positive charge still affects the electrons around the anion. Thus, the anion electrons' orbitals m...
Thu Nov 01, 2018 11:34 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and lone pairs
Replies: 2
Views: 135

### Re: Formal Charge and lone pairs

You should count each paired electron as one, and you should also see the bonds as having two electrons. The formula to find the formal charge is the following. Formal charge = valence electrons - (lone electrons + 0.5(bond electrons)) Therefore, although each bond has two electrons, you will be add...
Thu Nov 01, 2018 11:18 pm
Forum: Quantum Numbers and The H-Atom
Topic: Test #2 Question
Replies: 1
Views: 110

### Re: Test #2 Question

The possible quantum numbers of a 3p orbital include the following.

n=3
l=1
m(l)=-1, 0, 1
m(s)=-0.5, 0.5

These may be written as the following sets of {n, l, m(l), m(s)}.

{3, 1, -1, 0.5}
{3, 1, 0, 0.5}
{3, 1, 1, 0.5}
{3, 1, -1, -0.5}
{3, 1, 0, -0.5}
{3, 1, 1, -0.5}
Sun Oct 28, 2018 6:12 pm
Forum: Administrative Questions and Class Announcements
Replies: 3
Views: 173

1. You can check your grades via CCLE. If you are curious about a certain grade that isn't posted, you may want to consider asking your TA about it directly. 2. There is no curve. Rather, grades are assigned based upon the class average out of 500 points. This is not calculated until after all the p...
Sat Oct 27, 2018 3:03 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Affinity [ENDORSED]
Replies: 7
Views: 317

### Re: Electron Affinity[ENDORSED]

Yukta Italia 3I wrote:So are elements with high electron affinity most likely to form anions?

Elements with a high electron affinity are more likely to form anions than elements with a lower electron affinity.
Sat Oct 27, 2018 3:00 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Ml Meaning
Replies: 3
Views: 191

### Re: Ml Meaning

m(l) refers to the different orbitals in a subshell l. The s-subshell (l = 0) has one orbital, so m(l) has the value of 0. The p-subshell (l = 1) has three orbitals, so m(l) has the values of -1, 0, +1. The d-subshell (l = 2) has five orbitals, so m(l) has the values of -2, -1, 0, +1, +2. This patte...
Sat Oct 27, 2018 2:47 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum Numbers
Replies: 5
Views: 220

### Re: Quantum Numbers

In addition to what others have said I also recommend taking into consideration Hund's Rule and the electron configuration exceptions Lavelle mentioned (Cr and Cu) whenever asked anything about electron spin even if you may not know the specific spin of an electron in an orbital.
Sun Oct 21, 2018 11:48 pm
Forum: Properties of Light
Topic: Test 2 Equations
Replies: 14
Views: 501

### Re: Test 2 Equations

I believe most equations that you need will be given. However, I heard from a TA that you should memorize equations utilizing the Rydberg constant.
Mon Oct 15, 2018 10:00 pm
Forum: DeBroglie Equation
Topic: Velocity using de Broglie equation
Replies: 2
Views: 119

### Re: Velocity using de Broglie equation

(lambda)=c(nu) really only works for photons and electromagnetic radiation because it incorporates the speed of light. Neutrons do not travel at the speed of light. When dealing with objects that have rest mass, you should use DeBroglie's equation.
Mon Oct 15, 2018 9:52 pm
Forum: Einstein Equation
Topic: Question regarding wavelength
Replies: 5
Views: 199

### Re: Question regarding wavelength

Which of these equations you use ultimately depends on the information you are given. However, they should both be used when dealing with the wavelengths of electromagnetic radiation. Therefore, yes, you would specifically use these equations when dealing with photons.
Mon Oct 15, 2018 8:42 pm
Forum: DeBroglie Equation
Topic: 1B.15
Replies: 1
Views: 90

### Re: 1B.15

The problem with using (lambda) = hc/E in this case is that it can only be applied to light or something without rest mass. Because the electron has rest mass, DeBroglie's equation must be used. (lambda) = hc/E can be used to find the wavelengths of electromagnetic radiation, whereas DeBroglie's equ...
Sun Oct 14, 2018 8:01 pm
Forum: Properties of Light
Topic: 1A.3 Atomic Spectra
Replies: 2
Views: 54

### Re: 1A.3 Atomic Spectra

Plasma is defined as being an ionized gas consisting of free electrons and positive ions. Plasma is created when a gas is exposed to high temperatures, or as would occur in this case, an electrical current. Because the current makes the atoms in the gas move very quickly, the electrons get knocked o...
Sun Oct 14, 2018 7:45 pm
Forum: Photoelectric Effect
Topic: Sodium metal surface
Replies: 4
Views: 208

### Re: Sodium metal surface

For the work function, I got 1.506 x 10^5 J, but on the post assessment survey for photoelectric effect, the answer showed up as wrong. Would the frequency be (1.99 x 10^-19)/(6.626 x 10^-34) = 3.01 x 10^-14 Hz? I'm not sure about your first question. However, for your second question consider the ...
Sun Oct 14, 2018 7:31 pm
Forum: Einstein Equation
Topic: Numbers to memorize [ENDORSED]
Replies: 37
Views: 1760

### Re: Numbers to memorize[ENDORSED]

I recommend memorizing whichever constants and formulas you can, but don't stress about it too much. I can recall hearing that a formula sheet would be provided, but you should still play around with all the formulas just to make sure you understand everything before the exam.
Sun Oct 14, 2018 7:25 pm
Forum: Properties of Light
Topic: Problem A9
Replies: 5
Views: 118

### Re: Problem A9

To find the frequency for 2.5 nm use the equation (speed of light)=(wavelength)(frequency). You can start off by converting the wavelength to meters so you're using proper SI units. You need to do this because you're also using the speed of light in meters. Next, arrange the equation as (speed of li...
Sun Oct 07, 2018 7:26 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Replies: 7
Views: 611

Avogadro's constant still applies. For example, in chlorine gas (Cl2), there are 6.022 * 10^23 molecules of Cl2 per mol. Avogadro's constant can refer to the number of atoms, molecules, or formula units depending on the substance in question.
Fri Oct 05, 2018 11:58 pm
Forum: Molarity, Solutions, Dilutions
Topic: Problem G.25
Replies: 1
Views: 131

### Re: Problem G.25

So this problem was really easy at the beginning, but it quickly turned hard at the end. The question is " G.25 Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this que...
Fri Oct 05, 2018 11:34 pm
Forum: SI Units, Unit Conversions
Topic: SI Units on tests
Replies: 5
Views: 271

### Re: SI Units on tests

Is the conversion between US units and SI units given in the tests? Thanks! In response to your question, I think it would be very likely that these conversions would be given if they are necessary. I cannot say for certain whether or not this is the case, though. I recommend asking during office h...
Mon Oct 01, 2018 1:18 pm
Forum: SI Units, Unit Conversions
Topic: Office Hours [ENDORSED]
Replies: 2
Views: 106

### Re: Office Hours[ENDORSED]

I do believe office hours start this week (Week 1), and I think peer learning sessions start next week (Week 2).